The difference between the two has been explained on the list. Please
read and internalize that explanation.  In the meantime, have you
reviewed what the OSes actually present as the TZ name? I note that
MacOS presents both.

Could you please be more specific and provide an example?

MacOS 12.3.1 will take as input Kyiv and Kiev.  This is also true for certain older releases, I believe.  And this is a key point: most modern operating systems don't simply present or allow only the distributed database keys.

Eliot